Skin Flashcards
Define stroma
The supportive tissue of an epithelial organ, tumour, gonad, consisting of connective tissues and blood vessel
Why are the liver and lungs susceptible to pathological fibrosis
Delicate structures due to little connective tissue
Describe abscess formation
Caused by infection with staphylococci or excessive neutrophil infiltration
Focal collection of pus (from recruitment of many neutrophils and collection of dead cells and fluid )
Characterised by a necrotic core surrounded by neutrophils and fibroblasts
Can become walled off and require draining
Heals with a scar
Causes of Chronic inflammation
Consequence of persistent infection that failed to be elimated during initial period of acute inflammation
Due to autoimmune disease/hypersensitivity
Most viruses
Prolonged exposure to toxins such as silica , high plasma lipid conc
Cells involved in chronic inflammation
Macrophages , lymphocytes , plasma cells , eosinophils and mast cells
Name the mediators released by macrophages
TNF-alpha
IL-1
What are lable , stable and permanent tissue types?
Labile cells can replicate throughout their entire life So the tissue is capable of resolving
Stable cells are non-dividing in normal circumstances but are capable of regeneration ; can resolve or scar
Permanent cells are non-dividing ; always scar and loose their function
Describe the process of healing by fibrosis
Granulation of tissue via the action of macrophages, fibroblasts and angiogenesis
Fibrosis and scar formation ; fibroblasts lay down matrix and increase in collagen present to form scar
Remodelling - less vessels and collagenous scar remains
Describe the process of wound healing
Inflammatory phase
acute inflammation , arrival of macrophages to produce growth factors
Proliferative phase
Granulation tissue - fibroblasts secret matrix components and GFs to stimulate angiogenesis
Epithelial cells regrow over wound
Remodelling phase
reorganisation of matrix to restore function
wound contraction due to collagenases breaking down collagen to orientate maximal tensile strength ; this brings the wound edges together
Compare resolution and repair
Resolution arises from damage to parenchyma in labile/stable tissue
repair arises from damage to parenchyma and storm (or in brain/muscle)
resolution removes damaging stimulus via the action of inflammatory cells mediators and pus ; injured cells replaced by regeneration
repair replaces damaged tissue with connective tissue ; this results in scar and granulation tissue
resolution leads to restoration of function with minimal evidence of damage ; repair leads to loss of function
What are growth factors?
Hormone-like molecules that stimulate proliferation, differentiation and maturation of cells
they attract endothelial cells and fibroblasts - involved in angiogenesis and production of ECM
Name 2 examples of pathological fibrosis
when repair leads to disease
liver cirrhosis
interstitial fibrosis in lungs
Describe the macrophages role in chronic inflammation
macrophage activated by microbes, dead cells or activated T cells
Tissue injury and inflammation :
reactive oxygen and nitrogen species ; proteases ; cytokines ; coagulation factors
fibrosis :
growth factors ; fibrogenic cytokines ; agiogenesis factors
Describe the interaction between macrophages and T cells to prolong chronic inflammation
Activated T lymphocyte produces IFN-γ which activates macrophages
macrophafges in turn produce cytokines which activate T lymphocytes
